x86/spec: Actually do the check for in_use on ENABLE_IBRS

Orabug: 27344012
CVE: CVE-2017-5715
Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>

diff --git a/arch/x86/include/asm/spec_ctrl.h b/arch/x86/include/asm/spec_ctrl.h
index 5f7e27644a813672e86ad340cabff2e05c87bf88..26f1fac1fee9ff13e6715fb48e9f4d055603d423 100644 (file)
--- a/arch/x86/include/asm/spec_ctrl.h
+++ b/arch/x86/include/asm/spec_ctrl.h
@@ -128,7 +128,10 @@
        add $(32*8), %rsp;
 
 .macro ENABLE_IBRS
-ALTERNATIVE "", __stringify(__ASM_ENABLE_IBRS), X86_FEATURE_SPEC_CTRL
+       testl   $SPEC_CTRL_IBRS_INUSE, use_ibrs
+       jz      7f
+       __ASM_ENABLE_IBRS
+7:
 .endm
 
 .macro ENABLE_IBRS_CLOBBER